1. Field of the Invention
The present invention relates to an overrun prevention technology for a vehicular wiper device. In particular, the present invention relates to a wiper control device and a wiper control method, which are effective to prevent a phenomenon in which an overrun state is brought about by the outward movement of a blade distal end at an upper reversal position due to the deflection generated in a wiper arm or a wiper blade during high-speed running.
2. Description of the Related Art
The following wiper system is conventionally widely used for automobile wiper devices. The wiper system detects a current position of a wiper blade (hereinafter, abbreviated as “blade”) on a glass surface and causes the blade to perform a reciprocating wiping operation between an upper reversal position and a lower reversal position based on the detected data. With the wiper system described above, an operation of a wiper driving motor is controlled so that a direction of the operation of the blade is reversed at the predetermined upper reversal position and lower reversal position. The wiper driving motor is driven by an on-vehicle control device. The operation of the wiper driving motor is controlled so that a motor shaft of the wiper driving motor is stopped at an angle corresponding to the upper or lower reversal position.
In the conventional wiper system as described above, the control is performed so as not to change an operating angle of the motor shaft during running in a normal state. In this manner, the overrun of the blade (state in which the blade travels beyond a predetermined stop position) is prevented from occurring at the upper or lower reversal position. During high-speed running, however, a wiper arm, the blade, or a link mechanism is deflected against a wind generated by running. As a result, there arises a problem in that a blade distal end is disadvantageously moved outward when the direction of the operation of the blade is reversed at the upper reversal position. Specifically, even if the motor shaft is controlled to stop at a predetermined angle, there inevitably arises a problem of the occurrence of the overrun state due to the outward movement of the blade distal end during high-speed running.
On the other hand, if a wiping angle during a normal wiping operation is set small in view of the overrun occurring during the high-speed running, the problem due to the outward movement of the blade distal end can be avoided. However, the reduced wiping angle during the normal wiping operation has the undesirable effects of narrowing a field of view of a driver when it rains. In view of the problems described above, a system capable of preventing the overrun during the high-speed running and ensuring the field of view of a driver during the normal wiping operation is desired.